Send Mail is not working in Android 7.0

Hi All

Have a Nice day...

In My project i am sending mail through unity. Actually Mail is sending in pc and also in mobiles android version 8.0. But When i test my send mail option in Android 8.0 Samsung j3 prime.

Mail is not send from that mobile. But It is very well working in other mobiles. This is my below code..

Code (CSharp):

1. public void Start() {
2. using (var mail = new MailMessage {
3. From = new MailAddress(sender),
4. Subject = "test subject",
5. Body = "Hello there!"
6. }) {
7. mail.To.Add(receiver);
8. var smtpServer = new SmtpClient(smtpHost) {
9. Port = 25,
10. DeliveryMethod = SmtpDeliveryMethod.Network,
11. EnableSsl = true,
12. UseDefaultCredentials = false,
13. Credentials = (ICredentialsByHost)new NetworkCredential(sender, smtpPassword)
14. };
15. ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
16. smtpServer.Send(mail);
17. }
18. }
19. }

i am sending throuh gmail. It s working in all mobiles excep Android 8.0 Samsung j3 prime.

What i have to do for that?